1. Technical Field of the Invention
The present invention relates to cellular telephone networks and, in particular, to the distributed storage and delivery of data associated with cellular telephone network supported subscriber data services (such as short message, facsimile, voice mail and electronic mail delivery).
2. Description of Related Art
Reference is now made to FIG. 1 wherein there is shown a block diagram of a conventional digital cellular telephone network 10. The network 10 supports one or more subscriber data services (such as short message, facsimile, voice mail and electronic mail delivery) for use by subscribers in conjunction with their conventional cellular telephone service. The purpose of the subscriber data services is to provide a means for transferring subscriber data messages between message entities (MEs) 12 using the communications environment provided by the cellular telephone network 10.
The message entities 12 participating in the subscriber data service comprise data terminals (DTs) 14 connected to the fixed telephone network 16 (comprising a public switched telephone network (PSTN) or other equivalent/similar telephone network). The message entities 12 further comprise the subscriber mobile stations (MS) 18 operating within the cellular telephone network 10. Subscriber data messages must originate with or terminate at one of the subscriber mobile stations 18.
Multiple message centers (MC) 20 are provided and connected to the fixed telephone network 16 and to the cellular telephone network 10. Each message center 20 is a multi-media platform that functions as a store and forward/retrieve center for receiving and delivering subscriber data messages between the message entities 12. When a subscriber data message is originated, it is first sent to a message center 20 associated with that addressor subscriber. The message is then forwarded to another message center 20 associated with the addressee subscriber. At that point, the message is then delivered to (for example, forwarded to or retrieved by) the addressee message entity at an appropriate time.
The cellular telephone network 10 further includes a plurality of base stations 24 for effectuating radio frequency communications over an air interface 26 with the mobile stations 18. Each base station 24 is connected to a mobile switching center (MSC) 30. The mobile switching center 30 operates to control base station 24 operation, maintain a record (in a home location register 42 and a visitor location register--not shown) of mobile station 18 operating parameters and location within the network 10 and switch, either within the network 10 or with the fixed telephone network 16, those cellular telephone calls originated by or terminated at the mobile stations 18. The mobile switching centers 30 are further connected to the message centers 20 used in providing the subscriber data services.
A mobile station 18 is typically assigned a "home" message center 20 in much the same way that the mobile station is assigned a home location register 42. It is in this message center 20 that a mailbox 46 assigned to the given mobile station is maintained. Any subscriber data message intended for delivery to that given mobile station 18 passes through, for store and forward/retrieve delivery, the mailbox 46 assigned to and maintained in the associated home message center 20 for that given mobile station. Inefficiencies with this "home" message center 20 based network architecture and topology, however, often arise in connection with roaming mobile stations 18.
First, with respect to message center 20 store and forward operation, all subscriber data messages are initially stored in the home message center (of a home service area within the cellular telephone network 10h) for the addressee roaming subscriber mobile station 18. This message center 20 then must query the home location register 42 for that subscriber mobile station 18 in order to obtain location information, and then attempt to forward the subscriber data message over the network 10 to the roaming subscriber mobile station in a visited service area within the cellular telephone network 10v. Due to latency in updating the location information, or the mobile station being in inactive mode, or congestion in the network or air interface, forwarding of the subscriber data message may fail. Failure of the message forwarding operation results in a waste of valuable network communications resources and added user/service provider costs. This is especially a problem with subscriber data messages (such as facsimile, voice or the like) which require the establishment of a circuit connection to effectuate delivery.
Second, with respect to message center 20 store and retrieve operation, all subscriber data messages are again initially stored in the home message center (of a home service area within the cellular telephone network 10h) for the addressee roaming/moving subscriber mobile station 18. This message center 20 then must then be queried by the roaming subscriber mobile station 18 from the visited service area within the cellular telephone network 10v to collect the stored messages. When roaming, in particular, this querying operation to retrieve messages can be costly and inefficient. This is especially a problem with subscriber data messages (such as facsimile, voice or the like) which require the establishment of a circuit connection to effectuate delivery.
What is needed then is a more efficient network architecture and topology for handling stored subscriber data message delivery (either forwarding or retrieval) to roaming/moving subscriber mobile stations.